The wettest weather in at least 20 years boosted production from hydro-electric plants, leaving Sweden and Norway with some of the lowest power prices in the world.

The resulting glut in the most important raw material for making the virtual coins coincided with a year when the price of Bitcoin almost quadrupled.

With operations sometimes consuming as much power as that used by 70,000 households, the price of lecky is a key concern. It seems the Nordics are giving China, Kazakhstan and Canada a run for their money.

Philip Salter, head of operations at Hong Kong-based Genesis Mining, which operates a data centre in Boden, Sweden. "There were times we were not making any profit at all, but during the last year our profitability has more than tripled."

Unusually wet weather along with mild temperatures boosted hydro reservoirs across Nordic region to the highest level in more than 20 years, leaving the area awash in generation capacity. The result is power prices close to zero for extended periods. Average prices this year are about a third of those in Germany, Europe's biggest power market.